Note: On some systems, the program installed as /bin/sh is
not a Posix shell (it may be a variant of csh or a very buggy
implementation of Posix sh). On such systems, you should use a
different shell to run configure, such as:

% /usr/local/bin/bash ../configure --config-shell /usr/local/bin/bash

The null Device Your system must have /dev/null. Information
directed to /dev/null should simply disappear from the universe. As
a special "Green Software" measure, we have made provisions that
will enable your computers to convert that discarded information into
heat, which you may use to supplement conventional heating
systems.

2.2 Tools Used Internally by arch

The remaining tools are used internally by arch itself. They don't
necessarily need to be on your PATH – when you build arch from
source, run the configure script:

% ./configure --help

and

% ./configure --help-options

for information about how to point arch to the correct versions.

GNU Tar You must have GNU tar. arch invokes tar internally to
pack and unpack files that it stores in archives. It is important
that all versions of arch use a compatible version of tar, for
which purpose GNU tar was chosen.

GNU diff and GNU patch After much deliberation, I've decided to go
ahead and rely on the GNU versions of diff and patch.
Specifically, you need a version of diff that can generate "unified
format" output (option -u) and a version of patch that
understands that format and that understands --posix. (It would be
trivial to use "context diffs" and, thus, standard diff and
patch, however, unified diffs are much easier to read, and I'm
hoping that picking specific implementations of these critical
sub-components will help contribute to the long-term stability of
arch.)